The prior art has disclosed various devices to raise the lower objects by the use of cables which wind around a winch drum. Battens system which raise and lower stage sceneries and cranes in the construction industry are but two examples of such devices.
Till now, such devices have not been completely safe, because there is no automatic way of stopping an object being lowered or raised by cables whenever said object contacts a person or other obstacle in its path. In the case of a theatre battens system, an operator is needed to warn stage hands and actors of descending scenery and constantly look after the same.